Light source device including a planar light source having a single, substantially continuous light emission area and display device incorporating the light source device

ABSTRACT

A red light source comprising an array of LEDs  102 R that emit light of a red color, a green light source comprising an array of LEDs  102 G that emit light of a green color, and a blue light source comprising an array of LEDs  102 B that emit light of a blue color are deployed about the periphery of a dichroic prism  101 . A liquid crystal display element is illuminated by a light source device configured such that the light from the respective light sources is synthesized into white light by the dichroic prism, and projection type liquid crystal display devices and the like are configured.

TECHNICAL FIELD

The present invention relates to the configuration of a light sourcedevice in a display device for the magnification and projection ofimages displayed in liquid crystal display elements, and to theconfiguration of a display device using that light source device.

BACKGROUND ART

The technology disclosed in Japanese Patent Application Laid-Open No.H5-13049/1993, as published, may be cited as first prior art forminiaturizing projection type liquid crystal display devices whichmagnify, project, and display images of liquid crystal display elements.

Disclosed in this publication is the configuration of a display devicewherein three liquid crystal display elements are deployed about theperiphery of a dichroic prism, the liquid crystal display elements areilluminated by flat-panel fluorescent tubes emitting different colors oflight, respectively, deployed on the back sides of the liquid crystaldisplay elements, and images of the several colors synthesized by thedichroic prism are projected on a screen by a projection lens.

As second prior art for miniaturizing projection type liquid crystaldisplay devices, a configuration may be cited wherein only one liquidcrystal display element is used, that liquid crystal display element isilluminated from the back side thereof by a lamp such as a metal halidelamp, and the image of the liquid crystal display element is projectedonto a screen by a projection lens.

With the first prior art, cited above, however, because three liquidcrystal display elements are used, costs becomes high, which is aproblem, and an adjustment mechanism become necessary for keeping theimages of the three liquid crystal display elements from shifting out ofplace, which makes it very difficult to realize further miniaturizationin the display devices, which is also a problem.

With the second prior art, cited above, moreover, the light source is awhite light source, making it necessary to have color filters in thepixels of the liquid crystal display element in order to project colorimages. Three pixels, namely a red, a green, and a blue pixel arenecessary in order to generate colors, whereupon display imageresolution deteriorates, and, since light other than that of thetransmission wavelength is absorbed by the color filters, the displayimages become dark, which is a problem. In addition, a high voltage isrequired for lighting the metal halide lamp, which means that the powersupply circuit becomes large, thus making it very difficult tominiaturize the display device, which is a problem.

DISCLOSURE OF THE INVENTION

With the foregoing in view it is an object of the present invention touse only one liquid crystal display element, in order to miniaturize thedisplay device, and to miniaturize the overall display device by makingthe light source device compact.

It is a further object to provide, even in a display device using asingle liquid crystal display element, a display device wherein thelight from the light source device is used with high efficiency, andwhich is capable of displaying images of high resolution.

The light source device in accordance with first aspect comprises afirst light source for emitting light of a first color, a second lightsource for emitting light of a second color, and a third light sourcefor emitting light of a third color, characterized in that the lightfrom the first light source, the light from the second light source, andthe light from the third light source are synthesized by a colorsynthesizing optical system.

According to the configuration described above, there is a benefit inthat, because light from light emitting elements exhibiting high lightemission efficiency in the several colors can be synthesized, a whitelight source that is small and bright can be configured.

The light source device in accordance with second aspect is the lightsource device described in the first aspect, characterized in that thefirst color is a color in the region from orange to red, the secondcolor is a color in the region from green to yellow-green, and the thirdcolor is a color in the blue region.

According to the configuration described above, there is a benefit inthat, because light from light emitting elements exhibiting high lightemission efficiency in the several colors can be synthesized, a whitelight source that is small and bright can be configured.

The light source device in accordance with third aspect is the lightsource device described in the first aspect or the second aspect,characterized in that the color synthesizing optical system is adichroic prism.

With a dichroic prism, it is possible to make the optical axes of thethree colors coincide in a condition wherein there is almost no lightquantity loss.

The light source device in accordance with forth aspect is the lightsource device described in any one of the first to third aspects,characterized in that the first, second, and third light sources arelight emitting diodes.

According to the configuration described above, there is a benefit inthat, because the light source can be lit with a low voltage DC powersupply of 3 V or so, a small white light source can be configured thatincludes the power supply as well.

The light source device in accordance with fifth aspect, is the lightsource device described in the forth aspect, characterized in that aplurality of the light emitting diodes are deployed two-dimensionally inthe first, second, and third light sources, respectively.

According to the configuration described above, there is a benefit inthat a small white light source can be configured which emits light in aplanar form.

The light source device in accordance with sixth aspect is the lightsource device described in the fifth aspect, characterized in thatlenses are deployed between the first, second, and third light sourcesand the color synthesizing optical system.

According to the configuration described above, there is a benefit inthat the light emitted from the light emitting diodes can be convertedto light of high parallelism, and a small white light source can beconfigured wherewith the light is of high parallelism.

The light source device in accordance with seventh aspect is the lightsource device described in the fifth aspect, characterized in that lensarray elements are deployed between the first, second, and third lightsources and the color synthesizing optical system.

According to the configuration described above, there is a benefit inthat the light emitted from the plurality of light emitting diodes canbe converted to light of high parallelism, and a small white lightsource can be configured wherewith the light is of high parallelism.

The light source device in accordance with eighth aspect is the lightsource device described any one of the first to third aspects,characterized in that each of the first, second, and third light sourcesis a planar light source.

By planar light source, here, is meant a light source having a single,substantially continuous light emission region, capable of emittinglight with a uniform light emission quantity over a displayed areahaving vertical and lateral extent, wherewith light quantityirregularity can be prevented.

The light source device in accordance with ninth aspect is the lightsource device described in any one of the first to third aspects,characterized in that the first, second, and third light sources areflat-panel fluorescent tubes.

According to the configuration described above, there is a benefit inthat, because light from light emitting elements exhibiting high lightemission efficiency in the several colors can be synthesized, a whitelight source that is small and bright can be configured.

Also, because thin fluorescent tubes that emit light in planar form canbe used, the light source device can be miniaturized.

The light source device in accordance with tenth aspect is the lightsource device described in the ninth aspect, characterized in that prismarray elements are deployed between the flat-panel fluorescent tubes andthe color synthesizing optical system.

According to the configuration described above, there is a benefit inthat brightness can be enhanced in the frontal direction, and a lightsource device can be configured which is bright in the frontaldirection.

The light source device in accordance with eleventh aspect is the lightsource device described in the ninth aspect, characterized in that theprism array elements are configured from two mutually perpendicularprism arrays.

According to the configuration described above, there is a benefit inthat brightness can be enhanced in the frontal direction, and a lightsource device can be configured which is bright in the frontaldirection.

The light source device in accordance with twelvth aspect is the lightsource device described in the ninth aspect, characterized in that afirst polarization converter element is deployed between the first lightsource and the color synthesizing optical system, a second polarizationconverter element is deployed between the second light source and thecolor synthesizing optical system, and a third polarization converterelement is deployed between the third light source and the colorsynthesizing optical system.

By causing the directions of light polarization to coincide, lightquantity loss can be reduced when light output from the light sourcedevice passes through an optical material exhibiting polarizationdependency in its optical characteristics.

The light source device in accordance with thirteenth aspect is thelight source device described in the twelvth aspect, characterized inthat the polarization converter elements are reflecting polarizingplates.

Due to the reflecting polarizing plates, polarized light that isoscillating in a desirable direction is transmitted, while polarizedlight perpendicular thereto is returned to the light source side. Whenscattering occurs inside the light source, the direction of polarizationchanges, but it becomes possible to transmit polarized light convertedso that it oscillates in a desirable direction through the reflectingpolarizing plates. By repeating the reflection and scattering betweenthe reflecting polarizing plates and the light source in this manner,light emitted from the light source that is not polarized is convertedby the reflecting polarizing plates to polarized light wherewith thedirections of oscillation are aligned in the transmission axisdirections of the reflecting polarizing plates.

The light source device in accordance with fourteenth aspect is thelight source device described in any one of the first to third aspect,characterized in that the first, second, and third light sources areflat-panel electroluminescent elements.

According to the configuration described above, there is a benefit inthat, because thin planar-light emitting elements can be used, the lightsource device can be miniaturized.

The light source device in accordance with fifteenth aspect is the lightsource device described in the fourteenth aspect, characterized in thatthe electroluminescent elements are organic electroluminescent elementswherein the light emitting layer is an organic thin film.

According to the configuration described above, there is a benefit inthat, because the light source can be lit with a DC power supply, asmall white light source can be configured that includes the powersupply as well.

The light source device in accordance with sixteenth aspect is the lightsource device described in the fourteenth aspect, characterized in thatthe organic electroluminescent elements comprise optical resonators intheir light emitting layer structure.

According to the configuration described above, due to the opticalresonator structure, the spectrum width of the light emitted from theorganic electroluminescent elements can be narrowed to enhance colorpurity, and brightness in the normal direction (frontal direction) ofthe organic electroluminescent elements can also be enhanced.

The light source device in accordance with seventeenth aspect is thelight source device described in the fourteenth to sixteenth aspects,characterized in that a first polarization converter element is deployedbetween the first light source and the color synthesizing opticalsystem, a second polarization converter element is deployed between thesecond light source and the color synthesizing optical system, and athird polarization converter element is deployed between the third lightsource and the color synthesizing optical system.

The direction of polarization in the light emitted from a plurality oflight sources can be aligned, wherefore light loss in the opticalelements can be reduced by employing light modulating elements or otheroptical elements exhibiting polarization dependence in the opticalcharacteristics thereof as the light sources.

The light source device in accordance with eighteenth aspect is thelight source device described in the seventeenth aspect, characterizedin that the polarization converter elements are configured ofquarter-wave films and reflecting polarizing plates, the quarter-wavefilm is deployed on the light source side, and the reflecting polarizingplates are deployed on the color synthesizing optical system elementside.

By giving the polarization converter elements a structure such as this,the oscillation direction of the light emitted by the polarizationconverter elements can be aligned in a specific direction by thereflection of the light between the polarization converter elements andthe electroluminescent elements that are light sources provided with amirror-surface reflecting structure.

The light source device in accordance with nineteenth aspect is thelight source device described in any one the first to eighteenthaspects, characterized in that the first, second, and third lightsources light simultaneously.

According to the configuration described above, there is a benefit inthat the light emitted from the light source device can be made white.

The light source device in accordance with twentieth aspect is the lightsource device described in any one of the first to eighteenth aspects,characterized in that the first, second, and third light sourcesrepeatedly light in succession.

According to the configuration described above, there is a benefit inthat utilization is possible as a light source device in a sequential(or successive) color display type of display device.

A display device in accordance with twenty-first aspect has a lightmodulating element and the light source device described in any one ofthe first to twentieth aspects, characterized in that light from thelight source device is modulated in the light modulating element, andthe modulated light is magnified by a projection lens and displayed.

According to the configuration described above, there is a benefit inthat a small projection type liquid crystal display device can beconfigured.

The invention in accordance with twenty-second aspect is the displaydevice described in the twenty-first aspect, characterized in that thelight modulating element is a transmissive type liquid crystal element,the light source device is deployed opposite one face of the liquidcrystal element, and images formed in the liquid crystal element aremagnified by the projection lens and displayed.

Because this is a liquid crystal element, high-resolution images can bedisplayed, and images can be obtained with adequate brightness even whenmagnified and displayed by the projection lens.

The display device in accordance with twenty-third aspect is the displaydevice described in the twenty-second aspect, characterized in that amagnified virtual image of the image displayed by the liquid crystaldisplay element is viewed.

According to the configuration described above, there is a benefit inthat a virtual image viewing type of liquid crystal display device suchas a small head-mounted display can be configured.

The display device in accordance with twenty-forth aspect is the displaydevice described in the twenty-second aspect, characterized in thatcolor filters are formed in the pixels configuring the liquid crystaldisplay element.

According to the configuration described above, there is a benefit inthat a small liquid crystal display device can be configured which iscapable of color display.

The display device in accordance with twenty-fifth aspect is the displaydevice described in the twenty-second aspect, characterized in that thelight modulating element is a reflecting type light modulating element,and the light source device is deployed opposite the reflecting surfaceof the light modulating element.

Because the light source device is deployed in opposition to thereflecting surface of the light modulating element, a compact imagedisplay device can be obtained.

The display device in accordance with twenty-sixth aspect is a displaydevice having a light modulating element and the light source devicedescribe in any one of the first to twentieth aspects, wherein lightfrom the light source device is modulated in the light modulatingelement, and the modulated light is magnified by a projection lens anddisplayed as an image; characterized in that the light modulatingelement forms, with time division, a first color component image, asecond color component image, and a third color component image; thefirst light source in the light source device is lit during the timeinterval wherein the first color component image is being formed, thesecond light source in the light source device is lit next during thetime interval wherein the second color component image is being formed,and the third light source in the light source device is lit next duringthe time interval wherein the third color component image is beingformed; and a color image is displayed by the sequential display of thefirst, second, and third color components in the light modulatingelement, and by sequentially lighting of the first, second, and thirdlight sources corresponding to those sequential displays.

According to the configuration described above, color display ispossible, and a small projection type liquid crystal display device canbe configured wherein the display images are bright.

Also, a small virtual image viewing type liquid crystal display devicecan be configured which is capable of color display and wherein thedisplay images are bright.

The display device in accordance with twenty-seventh aspect is thedisplay device described in the twenty-sixth aspect, characterized inthat the light modulating element is a transmissive liquid crystalelement, the light source device is deployed opposite one face of theliquid crystal element, and images formed by the liquid crystal elementare magnified and displayed by the projection lens.

The formation of images by the liquid crystal element results in highresolution, wherefore clear or fine images can be obtained even whenthey are magnified and projected.

The display device in accordance with twenty-eighth aspect is thedisplay device described in the twenty-sixth aspect, characterized inthat virtual images that are magnifications of the images formed by theliquid crystal element are viewed.

By reducing light quantity loss and forming high-resolution images,clear or fine images can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram describing an optical system in a first embodimentof the light source device of the present invention, FIG. 1(a) being aview of the light source device as seen from above, and FIG. 1(b) beinga plan looking at a red light source from the dichroic prism side;

FIG. 2 is a diagram describing an optical system in a second embodimentof the light source device of the present invention, FIG. 2(a) being aview of the light source device as seen from above, and FIG. 2(b) beinga plan looking at a red light source from the dichroic prism side;

FIG. 3 is a diagram describing an optical system in a third embodimentof the light source device of the present invention looking at the lightsource device from above;

FIG. 4 is a diagram describing an optical system in a fourth embodimentof the light source device of the present invention, FIG. 4(a) being aview of the light source device as seen from above, and FIG. 4(b) beinga diagonal view of the red light source;

FIG. 5 is a diagram describing an optical system in a fifth embodimentof the light source device of the present invention looking at the lightsource device from above;

FIG. 6 is a diagram describing an optical system in a sixth embodimentof the light source device of the present invention looking at the lightsource device from above;

FIG. 7 is a diagram describing an optical system in a seventh embodimentof the light source device of the present invention looking at the lightsource device from above;

FIG. 8 is a diagram of the main optical system in a first embodiment ofthe display device in the present invention, as seen from above;

FIG. 9 is a diagram of the main optical system in a second embodiment ofthe display device in the present invention, as seen from above;

FIG. 10 is a detailed diagram of the display controller indicated inFIG. 9;

FIG. 11 is a timing chart indicating light source lighting and liquidcrystal display element display timing in the second embodiment of thedisplay device of the present invention;

FIG. 12 is a diagram of the main optical system in a third embodiment ofthe display device of the present invention, as seen from above;

FIG. 13 is a diagram of the main optical system in a fourth embodimentof the display device of the present invention, as seen from above; and

FIG. 14 is a diagram of the main optical system in a fifth embodiment ofthe display device of the present invention, as seen from above.

BEST MODE FOR CARRYING OUT THE INVENTION

Light source devices and display devices comprising those light sourcedevices in suitable embodiments of the present invention are nowdescribed with reference to the attached drawings.

(First Embodiment of Light Source Device)

A first embodiment of the light source device of the present inventionis described on the basis of FIG. 1. FIG. 1(a) is a diagram of the lightsource device as seen from above; FIG. 1(b) is a plan of a red lightsource as seen from the side of a dichroic prism serving as a colorsynthesizing optical system.

About the periphery of a dichroic prism 101 are deployed a red lightsource, a green light source, and a blue light source that areconfigured from two-dimensional arrays of light emitting diodes (LEDs).

The red light source is a structure wherein LEDs 102R (red) that emitlight of a wavelength in the red region are fixed to a board 103.Electric power is supplied to the LEDs 102R (red) from a DC power supply104 via a switch 105 and a variable resistor 106.

LEDs having a peak light emission wavelength of 620 nm can be used forthe LEDs 102R (red). In that case, the color of the emitted light willappear to be orange, but it is assumed that the color orange containsthe color red.

The red light source in this embodiment, as diagrammed in FIG. 1(b), isconfigured of an array of a total of 20 LEDs, 5 across and 4 down. TheLEDs are of a shape formed by molding a transparent resin, the tipswhereof have a lens shape, and the diameters whereof are 5 mm or so. Thenumber of LEDs depends on the size of the light source needed, and insome applications may be 1.

The green light source is a structure wherein LEDs 102G (green) thatemit light of a wavelength in the green region are fixed to a board 103.Electric power is supplied to the LEDs 102G (green) from a DC powersupply 104 via a switch 105 and a variable resistor 106. The number ofthese LEDs is the same as for the red light source diagrammed in FIG.1(b), namely 5 across and 4 down for a total of 20 LEDs.

LEDs having a peak light emission wavelength of 555 nm can be used forthe LEDs 102G (green). In addition, it is assumed that emitted lightthat appears yellow-green also contains the green color.

The blue light source is a structure wherein LEDs 102B (blue) that emitlight of a wavelength in the blue region are fixed to a board 103.Electric power is supplied to the LEDs 102B (blue) from a DC powersupply 104 via a switch 105 and a variable resistor 106. The number ofthese LEDs is the same as for the red light source diagrammed in FIG.1(b), namely 5 across and 4 down for a total of 20 LEDs.

LEDs having a peak light emission wavelength of 470 nm can be used forthe LEDs 102B (blue).

The light leaving the red light source is reflected by the redreflecting mirror of the dichroic prism 101. The light leaving the bluelight source is reflected by the blue reflecting mirror of the dichroicprism 101. And the light leaving the green light source is transmittedthrough the dichroic prism 101. In this manner, in the dichroic prism101, red, green, and blue light from the faces where no light source isdeployed is synthesized and output.

By controlling the current supplied to the LEDs of the various colors,the color of the light synthesized by the dichroic prism 101 can be madewhite, and hence a white light source can be configured. And byselecting the light source that is lit by the switches 105, light can beemitted in the single colors of red, green, and blue, and hence asingle-color light source device can be effected.

It is also possible to select two light sources to be lit, by theswitches 105, and thus to synthesize any two colors among red, green,and blue.

(Second Embodiment of Light Source Device)

A second embodiment of the light source device of the present inventionis described on the basis of FIG. 2. FIG. 2(a) is a diagram of the lightsource device as seen from above; FIG. 2(b) is a plan of a red lightsource as seen from the dichroic prism side.

In FIG. 2(b), the LEDs 102R (red) corresponding to lens elements 202Rconfiguring a lens array 201R are described by dotted lines. In FIG.2(a), moreover, the electrical circuitry for the light source, such asis diagrammed in FIG. 1(a), is not shown.

About the periphery of the dichroic prism 101 are deployed a red lightsource, green light source, and blue light source that are configured oftwo-dimensional arrays of light emitting diodes (LEDs).

The red light source is configured of an array of LEDs 102R (red) thatemit light of a wavelength in the red region, and a lens array 201Rdeployed between these LEDs and the dichroic prism. The lens array 201Ris configured by an array of lens elements 202R. The aperture shape inthe lens elements 202R is rectangular.

One lens element 202R corresponds with one LED 102R (red), and functionsto collimate divergent light that is emitted from the LED and to inputlight exhibiting high parallelism to the dichroic prism. The lenselements 202R in the red light source are designed so that there will belittle aberration at the peak light emission wavelength of the LEDs 102R(red). In addition, an anti-reflective film is formed so that reflectionat the surface is minimized at that wavelength.

The green light source is configured of an array of LEDs 102G (green)that emit light of a wavelength in the green region, and a lens array201G deployed between these LEDs and the dichroic prism. The lens array201G is configured by an array of lens elements (not shown) as in thecase of the red light source diagrammed in FIG. 2(b).

The lens elements in the green light source are designed so that therewill be little aberration at the peak light emission wavelength of theLEDs 102G (green). In addition, an anti-reflective film is formed sothat reflection at the surface is minimized at that wavelength.

The blue light source is configured of an array of LEDs 102B (blue) thatemit light of a wavelength in the blue region, and a lens array 201Bdeployed between these LEDs and the dichroic prism. The lens array 201Bis configured by an array of lens elements (not shown) as in the case ofthe red light source diagrammed in FIG. 2(b).

The lens elements in the blue light source are designed so that therewill be little aberration at the peak light emission wavelength of theLEDs 102B (blue). In addition, an anti-reflective film is formed so thatreflection at the surface is minimized at that wavelength.

In the light source device of this embodiment, the divergent lightemitted from the LEDs of the various colors is converted by the lensarrays to light exhibiting high parallelism and input to the dichroicprism, wherefore the light synthesized by the dichroic prism exhibitshigh parallelism, and a light source device can be provided wherewiththe emitted light exhibits high parallelism.

In FIG. 2(a), the shapes of the LEDs are represented as shapes formed bymolding a transparent resin so that the tips thereof are lens shaped,but such a lens shape is not always necessary.

(Third Embodiment of Light Source Device)

A third embodiment of the light source device of the present inventionis described on the basis of FIG. 3. FIG. 3 is a diagram of the lightsource device as seen from above.

About the periphery of a dichroic prism 101 are deployed a flat-panelfluorescent tube 301R (red) emitting light of a wavelength in the redregion, a flat-panel fluorescent tube 301G (green) emitting light of awavelength in the green region, and a flat-panel fluorescent tube 301B(blue) emitting light of a wavelength in the blue region.

These fluorescent tubes 301R, 301G, and 301B of the various colorscomprise light emitting bodies that, respectively, are a fluorescentbody that emits light which is red, a fluorescent body that emits lightwhich is green, and a fluorescent body that emits light which is blue.Each of these fluorescent tubes has a planar size such that the lightemission area is on the order of 19 mm×14 mm. The size of thefluorescent tubes is not limited to this size, and may be alteredaccording to the size of the light source required.

By employing the flat-panel fluorescent tubes 301R, 301G, and 301B aslight sources, moreover, light can be emitted uniformly over theprescribed surface area (based on a set value which is according to thesize of the area that is to be illuminated in the illuminated body thatis to be illuminated), and lens arrays or the like, such as are addedwhen LEDs 102R, 102G, and 102B are used, as in the light source devicein the second embodiment, become unnecessary. Hence outstanding benefitsare realized with a simple structure.

Depending on the surface area, moreover, rod-shaped fluorescent tubesmay be used, deploying such rod-shaped fluorescent tubes in parallel.

(Fourth Embodiment of Light Source Device)

A fourth embodiment of the light source device of the present inventionis described on the basis of FIG. 4. FIG. 4(a) is a diagram of the lightsource device as seen from above; FIG. 4(b) is a diagonal view of a redlight source.

About the periphery of a dichroic prism 101 are deployed a flat-panelfluorescent tube 301R (red) emitting light of a wavelength in the redregion, a flat-panel fluorescent tube 301G (green) emitting light of awavelength in the green region, and a flat-panel fluorescent tube 301B(blue) emitting light of a wavelength in the blue region.

Between the dichroic prism and the light source of each respective colorare inserted two prism arrays 401V and 401H. Each of these prism arraysis configured of rows of roof-shaped prisms extending in one direction.The prism array 401V and the prism array 401H are deployed so that thedirections of the respective prisms are mutually perpendicular.

In the case of the light source device in the third embodiment, lightleaving the flat-panel fluorescent tubes is input as divergent light tothe dichroic prism. In this embodiment, however, by deploying the prismarrays in front of the fluorescent tubes, light can be gathered in thenormal direction of the fluorescent tubes, and thus a light sourcedevice can be configured that exhibits high brightness in the frontaldirection.

Furthermore, by deploying a reflective polarizing plate between theprism array 401H and the dichoric prism corresponding to each color, thedirection of polarization of the light emitted from the flat-panelfluorescent tubes 301R, 301G, and 301B can be aligned. Using suchtechnology as this, the light emitted from the dichroic prism 101 can bemade linearly polarized light wherein the direction of oscillation isaligned.

(Fifth Embodiment of Light Source Device)

A fifth embodiment of the light source device of the present inventionis described on the basis of FIG. 5. FIG. 5 is a diagram of the lightsource device as seen from above.

About the periphery of a dichroic prism 101 are deployed an organicelectroluminescent element (EL) 501R (red) that emits light of awavelength in the red region, an organic electroluminescent element (EL)501G (green) that emits light of a wavelength in the green region, andan organic electroluminescent element (EL) 501B (blue) that emits lightof a wavelength in the blue region.

Each of these organic electroluminescent elements 501R, 501G, and 501B,respectively, comprises a light emitting layer structure 503R, 503G, and503B wherein are laminated, on a glass substrate 502, a transparentelectrode, an organic thin film layer structure, and a metal electrode.The light emitting layer structures are sealed by a sealing substrate504. The organic light emitting layers in the organic thin film layerstructures emit light when acted on by a DC electric field appliedbetween the transparent electrodes and the metal thin films. In terms ofthe materials for the organic light emitting films, it is possible toconfigure a red light source by using a material that emits light of ared color, a green light source by using a material that emits light ofa green color, and a blue light source by using a material that emitslight of a blue color.

The organic light emitting film for each color has a planar size suchthat the light emission area is on the order of 19 mm×14 mm. The size ofthe light emission area is not limited to this size, but may be alteredaccording to the size of the light source required.

Thus, by employing the organic EL elements 501R, 501G, and 501B, asuperiority is realized in that more uniform light emission can beeffected over a certain surface area as compared to when the LEDs 102R,102G, and 102B are employed as light sources as described earlier (inthe light source device in the first embodiment, for example). Theseorganic EL elements 501R, 501G, and 501B, moreover, are similar to theflat-panel fluorescent tubes 301R, 301G, and 301B employed in the lightsource device in the fourth embodiment described earlier, and arecategorized as planar light sources having a single, substantiallycontinuous light emission area.

(Sixth Embodiment of Light Source Device)

A sixth embodiment of the light source device of the present inventionis described on the basis of FIG. 6. FIG. 6 is a diagram of the lightsource device as seen from above.

About the periphery of a dichroic prism 101 are deployed an organicelectroluminescent element (EL) 601R (red) that emits light of awavelength in the red region, an organic electroluminescent element (EL)601G (green) that emits light of a wavelength in the green region, andan organic electroluminescent element (EL) 601B (blue) that emits lightof a wavelength in the blue region.

Each of these organic electroluminescent elements 601R, 601G, and 601B,respectively, comprises a light emitting layer structure 603R, 603G, and603B wherein are laminated, on a glass substrate 602, a transparentelectrode, an organic thin film layer structure, and a metal electrode.The light emitting layer structures are sealed by a sealing substrate604. The organic light emitting layers in the organic thin film layerstructures emit light when acted on by a DC electric field appliedbetween the transparent electrodes and the metal thin films. In terms ofthe materials for the organic light emitting films, it is possible toconfigure a red light source by using a material that emits light of ared color, a green light source by using a material that emits light ofa green color, and a blue light source by using a material that emitslight of a blue color.

The organic light emitting film for each color has a planar size suchthat the light emission area is on the order of 19 mm×14 mm. The size ofthe light emission area is not limited to this size, but may be alteredaccording to the size of the light source required.

Thus the basic configuration in this embodiment is the same as that ofthe light source device diagrammed in FIG. 5 in the fifth embodiment.The organic thin film layer structure therein is different, however, inthat, in this sixth embodiment, an optical resonator structure iscomprised in the organic thin film layer structure. With the opticalresonator structure, the spectrum width of the light emitted by theorganic EL elements 601R, 601G, and 601B can be narrowed and the colorpurity thereof enhanced, while the brightness in the normal direction(frontal direction) of the organic EL elements can also be enhanced.

(Seventh Embodiment of Light Source Device)

A seventh embodiment of the light source device of the present inventionis described on the basis of FIG. 7. The same symbols are used here todesignate the same configuring parts of the light source device as inthe sixth embodiment.

The light sources employed in this seventh embodiment are planar lightsources, specifically an organic EL element 601R that emits light of ared color, an organic EL element 601G that emits light of a green color,and an organic EL element 601B that emits light of a blue color. Each ofthese light emitting elements 601R, 601G, and 601B comprises an opticalresonator structure as in the light source device in the sixthembodiment. The light from the light emitting elements 601R, 601G, and601B of these three colors is synthesized by the dichroic prism 101.However, in the light source device in this seventh embodiment,polarization converter elements 607R, 607G, and 607B configured ofquarter-wave films (¼λ plates) 604R, 604G, and 604B and reflectingpolarizing plates 605R, 605G, and 605B are deployed between the dichroicprism 101 and the light emitting elements 601R, 601G, and 601B.

The quarter-wave film 604R and the reflecting polarizing plates 605R aredeployed in front of the organic EL element 601R emitting light that isred, the quarter-wave film 604G and the reflecting polarizing plate 605Gare deployed in front of the organic EL element 601G emitting light thatis green, and the quarter-wave film 604B and the reflecting polarizingplate 605B are deployed in front of the organic EL element 601B emittinglight that is blue. The reflecting polarizing plates 605R, 605G, and605B, respectively, function to transmit linearly polarized lightoscillating in a first direction, and to reflect linearly polarizinglight oscillating in a second direction that is perpendicular to thefirst direction.

The functions of the polarization converter elements 607R, 607G, and607B are now described, taking the organic EL element 601G that emitslight of a green color as an example.

It is here assumed that right-handed circularly polarized light from theorganic EL element 601G (indicated by R in the figure) is converted top-polarized light (indicated by P in the figure) that is linearlypolarized light by the quarter-wave film 604G. If it is further assumedthat the reflecting polarizing plate 605G is able to transmit thep-polarized light P, then this p-polarized light P is transmittedthrough the reflecting polarizing plate 605G.

The left-handed circularly polarized light (indicated by L in thefigure) from the organic EL element 601G, on the other hand, isconverted by the quarter-wave film 604G to s-polarized light (indicatedby S in the figure) that is linearly polarized light which isperpendicular to the p-polarized light. The s-polarized light isreflected by the reflecting polarizing plate 605G, converted back toleft-handed circularly polarized light by the quarter-wave film 604G,and returned to the organic EL element 601G.

The left-handed circularly polarized light that is returned to theorganic EL element 601G is converted to right-handed circularlypolarized light when it is reflected by the cathode electrode of theorganic EL element, etc., and then converted to p-polarized light by thequarter-wave film 604G. In this manner, the light emitted from theorganic EL element 601G is converted to linearly polarized light,wherein the direction of polarization is aligned, by the polarizationconverter element 607G configured of the quarter-wave film 604G and thereflecting polarizing plate 605G.

The technology for converting the polarization of light emitted fromsuch organic EL elements 601R, 601G, and 601B is disclosed inInternational Disclosure WO97/43686 and International DisclosureWO97/12276.

The quarter-wave film 604G and the reflecting polarizing plate 605G,respectively, may also be elements that function only in the greenwavelength band, or they may be elements that function across thevisible light wavelength region that includes red, green, and blue.

The light emitted from the organic EL element 601R that emits light thatis red and the organic EL element 601B that emits light that is blue,similarly, are converted to linearly polarized light P, wherein thedirection of oscillation is aligned, by the polarization converterelements 607R and 607B.

The quarter-wave film 604R and the reflecting polarizing plate 605Rcorresponding to the red color, or the quarter-wave film 604B and thereflecting polarizing plate 605B corresponding to the blue color, may beelements that, respectively, function only in the red or blue wavelengthbands, or they may be elements that function across the visible lightwavelength region that includes red, green, and blue.

The red, green, and blue light that has become linearly polarized lightis synthesized by the dichroic prism 101 and output from the dichroicprism 101 as linearly polarized light wherein the direction ofoscillation is aligned.

(First Embodiment of Display Device)

A first embodiment of the display device of the present invention isdescribed on the basis of FIG. 8. FIG. 8 is a diagram of the mainoptical system of the display device, as seen from above.

On the back side of a liquid crystal display element 701 is deployed thelight source device described in the fourth embodiment as the lightsource diagrammed in FIG. 4. The light source device is configured of adichroic prism 101, flat-panel fluorescent tube 301R (red), flat-panelfluorescent tube 301G (green), flat-panel fluorescent tube 301B (blue),and prism arrays 401V and 401H. White light resulting from the synthesisof red, green, and blue colors is directed onto the liquid crystaldisplay element 701.

The image displayed on the liquid crystal display element 701 ismagnified and projected onto a screen 706 by a projection lens 705.

The liquid crystal display element 101 has a liquid crystal layer 703that is sandwiched between glass substrates 704, whereon are formedcolor filters 702R, 702G, and 702B, in each pixel, for displaying colorimages. To make it easier to understand, this diagram is drawn withoutshowing the wiring or elements that drive the liquid crystal.

The display area on the liquid crystal display element 701 is 18.3×13.7mm (0.9 inch diagonally), for example. The size of this display area canbe altered as necessary, but the sizes of the light emission areas ofthe light sources for each color must also be altered to match the sizeof the display area.

In the light source devices of each color which employ flat-panelfluorescent tubes as described for the light source device in the fourthembodiment, reflecting polarizing plates may be deployed between thedichroic prism and the prism arrays.

(Second Embodiment of Display Device)

A second embodiment of the display device of the present invention isdescribed on the basis of FIG. 9 to 11. FIG. 9 is a diagram of the mainoptical system of the display device, as seen from above; FIG. 10 is adetailed block diagram of the control circuit in the display device; andFIG. 11 is a timing chart for the timing of light source lighting andliquid crystal display element displaying.

To the back side of a liquid crystal display element 801 is deployed thelight source device described in the second embodiment of the lightsource device that is diagrammed in FIG. 2. The light source device isconfigured of a dichroic prism 101, LED 102R (red), LED 102G (green),LED 102B (blue), and lens arrays 201R, 210G, and 201B.

The lighting of the LEDs of each color and the driving of the liquidcrystal display element are controlled by a display controller circuit802.

In FIG. 10, a detailed diagram of the display controller circuit 802 isgiven. This display controller circuit 802 is provided with framememories 810 corresponding to each color R, G, and B. Image data aretemporarily stored in the frame memories 810 of each respective color.From the image data stored in the frame memories 810, synchronizationsignals are extracted by a synchronization signal extractor unit 812,and synchronization is effected by clock signals from a clock 814. Theconfiguration is such that the synchronization signals are output to anoutput timing generator 816, and output both to an image outputcontroller 818 which controls the driving of the liquid crystal displayelement 801 and to a switching controller 820 that controls the drivingof the light emitting elements of each color.

To the image output controller 818 are input image data from the framememories 810, and prescribed images are formed on the liquid crystaldisplay element 801 by power supplied from an LCD (liquid crystaldevice) power supply circuit 822, based on the synchronization signalsnoted above.

Meanwhile, in the switching controller 820, in order to light the lightemitting elements of colors corresponding to the images displayed by theliquid crystal display element 801, signals are sequentially switchedand output to an R driver 824, a G driver 826, and a B driver 828. Thusthe sequential lighting of the LEDs 102R, 102G, and 102B, in an orderprescribed by RGB (and in synchronization with the order of imagedisplay to the liquid crystal display element 801) is repeated.

This control method is described with reference to FIG. 11.Red-component images, green-component images, and blue-component imagesare sequentially displayed within one field in the liquid crystaldisplay element 801. The timing of LED lighting and of images displayedon the liquid crystal display element is controlled so that while thered-component image is being displayed the red LED 102R is lit, whilethe green-component image is being displayed the green LED 102G is lit,and while the blue-component image is being displayed the blue LED 102Bis lit.

By performing color-sequence displays such as this, using the afterimage effect of the human eye, there ceases to be a necessity to providethe liquid crystal display element with color filters. The color filtersused in the liquid crystal display element 701 in the display device ofthe first embodiment diagrammed in FIG. 8 absorb light of wavelengthsother than the respective transmission wavelengths thereof. In contrastthereto, however, in the case of color-sequence display as in thisembodiment, the light utilization efficiency from the light source tothe screen can be enhanced.

In the display device of the first embodiment diagrammed in FIG. 8,moreover, the color-sequence display scheme described in the foregoingcan be employed instead of using color filters in the liquid crystaldisplay element 701 and the light utilization efficiency enhancedaccordingly.

In the display of color images by a color-sequence drive, as describedabove, furthermore, the light from the RGB light sources is output afterpassing through the dichroic prism 101, wherefore the light axes of thelight sources of the several colors coincide, and the liquid crystaldisplay element can be illuminated by the light sources of the severalcolors in the same direction, wherefore a benefit is realized in thatthe color is not dependent on visual angle.

(Third Embodiment of Display Device)

A third embodiment of the display device of the present invention isdescribed on the basis of FIG. 12. FIG. 12 is a diagram of the mainoptical system of the display device, as seen from above.

On the back side of a liquid crystal display element 701 is deployed thelight source device of the first embodiment diagrammed in FIG. 1. Thelight source device is configured of the dichroic prism 101, LED 102R(red), LED 102G (green), and LED 102B (blue), and the liquid crystaldisplay element 701 is illuminated by white light synthesized from thered, green, and blue light.

The display device in this embodiment is a display device wherewithvirtual images are viewed that pass through a lens 1001 and aremagnified by the liquid crystal display element 701.

(Fourth Embodiment of Display Device)

A fourth embodiment of the display device of the present invention isdescribed on the basis of FIG. 13.

On the back side of a liquid crystal display device 606 is deployed thelight source device described in the seventh embodiment as the lightsource device diagrammed in FIG. 7.

The light source device consists of the organic EL elements 601R, 601G,and 601B that comprise an optical resonator structure. On the front sideof the organic EL elements 601R, 601G, and 601B are deployed thequarter-wave films 604R, 604G, and 604B and the reflecting polarizingplates 605R, 605G, and 605B.

As described in the light source device in the seventh embodiment, lightoutput from the dichroic prism 101 is linearly polarized light P whereinthe direction of oscillation is aligned.

The liquid crystal display element 606 is provided with an input-sidepolarizing plate 610P and an output-side polarizing plate 610A. However,by aligning the transmission axis of the input-side polarizing plate610P with the direction of oscillation in the linearly polarized lightP, the absorption of light by the polarizing plate 610P can be reduced,the light quantity that can be transmitted through the liquid crystaldisplay element 606 can be increased, and the light from the lightsource device can be efficiently modulated by the liquid crystal displayelement 606.

The images displayed on the liquid crystal display element 606 aremagnified and projected onto a screen 609 by a projection lens 608.

In cases where the liquid crystal display element 606 is provided withcolor filters in each pixel, color images can be projected bysimultaneously lighting the red, green, and blue organic EL elements601R, 601G, and 601B, and illuminating the liquid crystal displayelement with white light.

In cases where the liquid crystal display element 606 is not providedwith color filters, on the other hand, color image displays can be madeby employing a color-sequence drive for lighting the red, green, andblue EL elements 601R, 601G, and 601B, such as described in the secondembodiment of the display device, in order, in one frame.

In displaying color images by such a color-sequence drive as notedabove, furthermore, the light axis of the light sources of each colorcoincide, and illumination can be done from the same direction,wherefore a benefit is realized in that there is no color dependence onvisual angle.

(Fifth Embodiment of Display Device)

A fifth embodiment of the display device of the present invention isdescribed on the basis of FIG. 14. FIG. 14 is a diagram of the mainoptical system of the display device, as seen from above.

The display device diagrammed in FIG. 14 has the same light sourcedevice and liquid crystal display device configuration as diagrammed inFIG. 13, with the only difference being the deployment of a half mirror1101 between a lens 1001 and the eye 1002 of an observer.

The half mirror 1101 enables magnified images of the liquid crystaldisplay element 701 to be viewed superimposed on the outside world 1102.

If there is no need to view the outside world, then a fully reflectingmirror may be used in place of the half mirror.

The light sources employed for effecting color-sequence drive in theembodiment aspects, particularly in the embodiment aspects of thedisplay device, are not limited to point light sources like LEDs, butmay be planar light sources such as organic EL elements or flat-panelfluorescent tubes, etc.

In the embodiments described in the foregoing, in terms of the form ofthe display device, the descriptions are for examples whereintransmissive type liquid crystal display elements are used. The presentinvention is not limited thereto or thereby, however, and opticaldevices are also provided by the present invention wherein reflectivetype liquid crystal display elements that reflect light from a lightsource, or light valves wherewith images are formed using a deformablemirror, or light modulating devices of a type that reflect light fromthe outside, such as spatial modulation elements, etc., are combined aslight modulating members or means together with light sources.

INDUSTRIAL APPLICABILITY

As based on the light source device of the present invention, asdescribed in the foregoing, by providing light sources wherewith thelight emission efficiency is maximized in wavelengths for red, green,and blue, respectively, and synthesizing the light from those lightsources with a dichroic prism, a benefit is realized in that a smalllight source device can be configured wherewith bright white light canbe generated.

By illuminating light modulating elements such as liquid crystal displayelements by such a light source device, a benefit is realized in that asmall display device can be configured. Furthermore, by lighting thelight sources for red, green, and blue light in order, and causing, insynchronization therewith, red-, green-, and blue-component images to bedisplayed on the liquid crystal display element or other lightmodulating element, a benefit is realized in that the brightness of asmall display device comprising a single light modulating element can beenhanced.

1. A light source device, comprising: a first light source for emitting first light of a first color; a second light source for emitting second light of a second color; a third light source for emitting third light of a third color; a first polarization converter for aligning a polarization direction of said first light by converting one polarization component to the other polarization component; a second polarization converter for aligning a polarization direction of said second light by converting one polarization component to the other polarization component; a third polarization converter for aligning a polarization direction of said third light by converting one polarization component to the other polarization component; and a color synthesizing optical system for synthesizing said first, second and third light of which the polarization directions are respectively aligned by said first, second, and third polarization converters, wherein the first polarization converter comprises a first reflecting polarizer positioned between the first light source and the color synthesizing optical system, and a first reflector provided inside the first light source so that polarized light that is returned to the first light source is reflected by the first reflector toward the first reflecting polarizer, the second polarization converter comprises a second reflecting polarizer positioned between the second light source and the color synthesizing optical system, and a second reflector provided inside the second light source so that polarized light that is returned to the second light source is reflected by the second reflector toward the second reflecting polarizer, the third polarization converter comprises a third reflecting polarizer positioned between the third light source and the color synthesizing optical system, and a third reflector provided inside the third light source so that polarized light that is returned to the third light source is reflected by the third reflector toward the third reflecting polarizer.
 2. The light source device according to claim 1, characterized in that said first color is a color in a region from orange to red, said second color is a color in a region from green to yellow-green, and said third color is a color in a blue region.
 3. The light source device according to claim 1, characterized in that said color synthesizing optical system is a dichroic prism.
 4. The light source device according to claim 1, characterized in that said first, second, and third light sources are light emitting diodes.
 5. The light source device according to claim 4, characterized in that lenses are deployed between said first, second, and third light sources and said color synthesizing optical system.
 6. The light source device according to claim 4, characterized in that lens array elements are deployed between said first, second, and third light sources and said color synthesizing optical system.
 7. The light source device according to claim 4, characterized in that a plurality of said light emitting diodes are deployed two-dimensionally in said first, second, and third light sources, respectively.
 8. The light source device according to claim 1, characterized in that said first, second, and third light sources are flat-panel fluorescent tubes.
 9. The light source device according to claim 8, characterized in that prism array elements are deployed between said flat-panel fluorescent tubes and said color synthesizing optical system.
 10. The light source device according to claim 8, characterized in that said prism array elements are each configured from two mutually perpendicular prism arrays.
 11. The light source device according to claim 1, characterized in that said first, second, and third light sources are flat-panel electroluminescent elements.
 12. The light source device according to claim 11, characterized in that said electroluminescent elements are organic electroluminescent elements having organic thin films as light emitting layers.
 13. The light source device according to claim 11, characterized in that said organic electroluminescent elements comprise optical resonators in light emitting layer structures thereof.
 14. The light source device according to claim 1, characterized in that said first, second, and third light sources light simultaneously.
 15. The light source device according to claim 1, characterized in that said first, second, and third light sources repeatedly light in order.
 16. A display device having: a light modulating element; and a light source device according to claim 1; characterized in that: light from said light source device is modulated in said light modulating element; and light so modulated is magnified by a projection lens and displayed.
 17. The display device according to claim 16, characterized in that: said light modulating element is a transmissive type liquid crystal element; said light source device is deployed opposite one face of said liquid crystal element; and images formed on said liquid crystal element are magnified by said projection lens and displayed.
 18. The display device according to claim 17, characterized in that magnified virtual images of images displayed by a liquid crystal display element are viewed.
 19. The display device according to claim 17, characterized in that color filters are formed in pixels configuring said liquid crystal display element.
 20. The display device according to claim 16, characterized in that said light modulating element is a reflecting type light modulating element, and said light source device is deployed opposite reflecting surface of said light modulating element.
 21. The display device according to claim 16, characterized in that: said light modulating element forms, with time division, a first color component image, a second color component image, and a third color component image; said first light source in said light source device is lit during time interval wherein said first color component image is being formed, said second light source in said light source device is lit next during time interval wherein said second color component image is being formed, and said third light source in said light source device is lit next during time interval wherein said third color component image is being formed; and a color image is displayed by sequential display of said first, second, and third color components in said light modulating element, and by sequential lighting of said first, second, and third light sources corresponding to those sequential displays.
 22. The display device according to claim 16, characterized in that said first color is a color in a region from orange to red, said second color is a color in a region from green to yellow-green, and said third color is a color in a blue region.
 23. The display device according to claim 16, characterized in that said color synthesizing optical system is a dichroic prism.
 24. The display device according to claim 16, characterized in that said first, second, and third light sources are light emitting diodes.
 25. The display device according to claim 24, characterized in that a plurality of said light emitting diodes are deployed two-dimensionally in said first, second, and third light sources, respectively.
 26. The display device according to claim 24, characterized in that lenses are deployed between said first, second, and third light sources and said color synthesizing optical system.
 27. The display device according to claim 24, characterized in that lens array elements are deployed between said first, second, and third light sources and said color synthesizing optical system.
 28. The display device according to claim 16, characterized in that each of said first, second, third light sources is a planar light source.
 29. The display device according to claim 16, characterized in that said first, second, and third light source are flat-panel fluorescent tubes.
 30. The display device according to claim 29, characterized in that prism array elements are deployed between said flat-panel fluorescent tubes and said color synthesizing optical system.
 31. The display device according to claim 29, characterized in that said prism array elements are each configured from two mutually perpendicular prism arrays.
 32. The display device according to claim 16, characterized in that said first, second, and third light sources are flat-panel electroluminescent elements.
 33. The display device according to claim 32, characterized in that said electroluminescent elements are organic electroluminescent elements having organic thin films as light emitting layers.
 34. The display device according to claim 32, characterized in that said organic electroluminescent elements comprise optical resonators in light emitting layer structures thereof.
 35. The display device according to claim 16, characterized in that said polarization converter further comprises a quarter-wave film, said quarter-wave film being deployed on sides toward said light sources; and said reflecting polarizer is deployed on sides toward said color synthesizing optical system element.
 36. The display device according to claim 16, characterized in that said first, second and third light sources light simultaneously.
 37. The display device according to claim 16, characterized in that said first, second, and third light sources repeatedly light in order.
 38. The display device according to claim 16, wherein polarization directions of the polarization components are perpendicular to each other.
 39. The display device according to claim 16, wherein rotational directions of the polarization components are opposite to each other.
 40. The light source device according to claim 1, wherein polarization directions of the polarization components are perpendicular to each other.
 41. The light source device according to claim 1, wherein rotational directions of the polarization components are opposite to each other.
 42. The light source device according to claim 1, characterized in that each of said first, second, and third light sources is a planar light source.
 43. The light source device according to claim 1, characterized in that said polarization converter further comprises a quarter-wave film, said quarter-wave film being deployed on sides toward said light sources; and said reflecting polarizer is deployed on sides toward said color synthesizing optical system element. 